A long-term study on the chronic toxicity of malonaldehyde (MA) when administered to mice at low levels will be completed. On the basis of a preliminary 90-day study in which dose-dependent liver lesions were observed throughout a range of 2 to 500 micrograms MA/g/day, doses of 0.1, 1 and 10 micrograms/g/day were selected for the long-term study. An effort will be made to develop an HPLC method for the determination of MA. The conventional method, which involves a reaction with thiobarbituric acid, is not specific for MA and hence is not entirely suitable for monitoring small concentrations of MA in animal tissues and in foods. Additional studies will be carried out on the binding of 14C-MA by DNA. These studies will be aimed at determining which bases are primarily involved, whether MA acts as a crosslinking agent, and whether it can be cleaved from deoxyribonucleotides.